It is well known in the art that some dental patients require restoration of teeth. In particular, there are some patients whose teeth are no longer present, or whose teeth have deteriorated to the degree that they cannot serve as a platform for the mounting of traditional dental prosthetics, e.g. bridges.
Implants, now in use for about forty years, are the standard way to attach fixed dental prostheses in place. One implant may support a single replacement tooth, usually cemented atop an abutment. Where several teeth are missing, two or more implants may be used.
In traditional implant-supported prosthesis installation, implants are first installed by an oral surgeon. He or she first examines the areas in which implants are needed, refers to conventional dental x-rays to learn if the underlying bone structure appears suitable to support implants. This information is, however, not fully revealed by conventional two-dimensional x-ray images. If bone structure is not adequate, additional surgery may be needed to enhance it. After any required bone enhancement, based on x-rays and personal judgment, the surgeon drills a cavity for each implant, using a manually held drill. Each implant is then screwed into place with a wrench. In most instances, the patient's dentist would carry out the remaining steps.
Unaided manual preparation of a jaw for implants is challenging, especially if done infrequently by a practitioner, because of the difficulty in estimating positions and angles accurately by eye, within a deep hole of small diameter in a patient's mouth. Even if the work is being done by an experienced dentist or oral surgeon, chances for location or orientation errors are great. By analogy with woodworking practice, some form of drill guide should be of considerable help in preparing implant cavities. Because of the necessary complexity of a guide adjustable to any patient and case, a guide customized for the patient and case is preferable.
One way to create a custom implant drill guide involves use of Cone Beam technology to capture an enhanced view of the upper and lower jaw region of a patient's head. The resulting imagery can show the bone structure and teeth in detail as well as the soft tissues. Using specially designed software that aids in predefining appropriate implant locations, the Cone Beam data can be used to create another set of data defining the location, orientation, and depth of each cavity to be prepared. From this, with use of a numerically controlled drilling tool, a patient- and case-customized drill guide is constructed. When properly mounted in the patient's mouth, guide holes in this unit align the drilling tool for its use in creating each predefined implant cavity. Each implant is then inserted and moved into its permanent location.
After installation of implants, traditional procedure varies, depending on how long a delay (of up to six months) is allowed for accommodation of the implant(s) by the bone of the jaw (osseointegration). Some implant manufacturers recommend loading implants immediately, others do not. If a healing delay is to be observed, a healing abutment—a metal extension washer with a domelike-top—is fastened to each implant by a screw in the threaded hole of the implant, and the gum flesh is sutured over the abutment.
On successful completion of the implant procedure, the patient returns to his Dentist for the later process steps. To install the prosthesis, tissue over the implants is reopened using a knife or a punch. The healing abutments are removed from the implants to reveal the surfaces on which the frame's attachment points will rest. Dental impressions are made of upper and lower jaws. Molds (positive models of the jaws) are made from these impressions, in a traditional procedure. The physical molds after being shipped to a dental laboratory are used to build up a prosthesis, in a traditional highly labor-intensive process demanding high skill level and long experience for good results.
The established paradigm for prosthesis construction, save for very small prostheses, involves constructing initially a rigid (therefore, heavy) metal structure which we shall refer to as the frame or framework. (Some sources refer to it as a bar.) It incorporates one short, hollow cylindrical attachment element for each implant. The attachment cylinders are connected using simple shapes. All is first modeled using hand-assembled solid and liquid plastics then cast in a suitable metal or alloy. After casting, if adjustment is required, it is customarily done using manual tools. Each attachment cylinder is positioned and oriented to fit snugly atop its corresponding implant and to accept a screw holding it to the implant. With these screws in place in all implants, the frame will be rigidly attached to the jaw. Since the attachments on the frame extend somewhat beyond the frame itself, when the frame is attached to the implants it stands slightly above the gum. This space is later filled with molded thermoplastic resin closely fitting the contour of the jaw.
After the frame is created, it is mounted to the model of the patient's corresponding jaw made by his or her dentist. Both models are then articulated on a conventional hinged metal mounting. A suitable type and size of artificial tooth for each replacement location is selected from a graded set of pre-molded teeth of each type (molar, bicuspid, etc.). The closed-mouth spacing between upper and lower jaw teeth is verified using the measurements made before restoration work was begun.
The remainder of the traditional prosthesis construction consists of firmly locating artificial teeth and fastening them in place, shaping thermoplastic resin smoothly over the outside of the frame and the gums, and preparing the clearance holes for the attachment screws.
Installation, as in most corrective dentistry, may require removal of small amounts of material from the prosthesis in places where it is tight (“milling-in”). If the implant-to-prosthesis connecting surfaces do not match exactly, within limits some grinding or filing can be done, as is also true for traditional prostheses. After the prosthesis has been fitted, the screw access holes needed to fasten prosthesis to implants will be filled with plastic resin and smoothed.
One group of limitations of prior-art procedures are those associated with unaided manual preparation of the mouth for, and placement of, dental implants:
a) The human jawbone is highly variable in thickness from location to location, and varies from person to person. Thus, for a given individual's jaw, certain implant locations are preferable to others because of bone strength variations.
b) For implant attachment strength, the optimal direction at which the implant should pass into the bone varies from one jaw location to another, and bone configurations are different from person to person. If the hole in the bone is drilled at an incorrect location and/or angle, the tip of the implant may pass through the bone and out the far side, weakening its attachment strength. Protruding implant tips also raise patient objections on cosmetic grounds.
c) Poor placement of implants can be a source of problems in installing and using a prosthesis. If implants exit the jaw out-of-parallel with one another it will be more difficult to align the prosthesis to the implants. In addition, when implant axes are far from parallel, biting forces will translate from purely compressive force to bending force more likely to fracture the bone.
d) Even if conventional x-ray images or computer tomographic (CT) scan images are available for a patient's jaw, a practitioner preparing a jaw for implants without some form of drilling guide must make on-the-spot decisions as to location, must estimate angles without visual help and in an irregularly shaped environment (the mouth), needs exceptional hand-eye coordination (even for a dentist), and must make exacting position estimates unaided.
Additional problems and limitations occur during design and construction of prostheses:
a) They are the most labor-intensive products used in dental practice, and require expensive metals and plastics. In traditional design the prosthesis frame is often heavy, since it may be modeled manually by fastening simple plastic shapes together with liquid plastic filler.
b) Fully trained and experienced technicians skilled in this work do not emerge from vocational schools and colleges. Most dental laboratories lack large enough and capable enough staffs to teach the full range of needed skills to each new employee. In short, automation of critical parts of the work is much needed.
c) Traditional prosthesis construction techniques employ materials that often must be chosen for ease in use during the largely manual construction process, rather than for their properties in the final product. Use of a heavy, rigid frame for prostheses is probably not optimal in the oral environment, where bones are brittle, teeth are hard and tough, but adjacent ligament and gum tissue are elastic and softer.
d) Certain difficulties and diseconomies occur because of the complexity of the process of acquiring and installing a quality prosthetic, variations from case to case reflected in the assembly process, and the ad hoc nature of the work.
Traditionally, a large proportion of communications between a dentist and others involved in restoration have been through physical transmission of bulky impressions or models of patients' jaws. Close proximity of dentists to supporting laboratory organizations has traditionally been desirable. New broadband communication technologies based on the Internet have enabled different ways of operating.
Other problems exist.
Related art includes the following patents:
U.S. Pat. No. 5,224,049, issued to Mushabac on Jun. 29, 1993
U.S. Pat. No. 5,368,478, issued to Andreiko et al. on Nov. 29, 1994
U.S. Pat. No. 5,453,009, issued to Feldman on Sep. 26, 1995
U.S. Pat. No. 5,740,800, issued to Hendrickson et al. on Apr. 21, 1998
U.S. Pat. No. 5,930,759, issued to Moore, et al. on Jul. 27, 1999
U.S. Pat. No. 6,032,119, issued to Brown et al. on Feb. 29, 2000
U.S. Pat. No. 6,199,115, issued to DiRienzo on Mar. 6, 2001
U.S. Pat. No. 6,287,119, issued to van Nifterick et al. on Sep. 11, 2001
U.S. Pat. No. 6,582,225, issued to Bergersen on Jun. 24, 2003
U.S. Pat. No. 6,786,726, issued to Lehmann et al. on Sep. 7, 2004
U.S. Pat. No. 6,821,123, issued to Andersson et al. on Nov. 23, 2004
U.S. Pat. No. 7,089,070, issued to Andersson et al. on Aug. 8, 2006
While these patents and other previous methods have attempted to solve the problems that they addressed, none have utilized or disclosed an improved system and method for the design, creation and installation of implant-supported dental prostheses, as does embodiments of the present invention.
Therefore, a need exists for an improved system and method for the design, creation and installation of implant-supported dental prostheses with these attributes and functionalities. The improved system and method for the design, creation and installation of implant-supported dental prostheses according to embodiments of the invention substantially departs from the conventional concepts and designs of the prior art. It can be appreciated that there exists a continuing need for a new and improved an improved system and method for the design, creation and installation of implant-supported dental prostheses which can be used commercially. In this regard, the present invention substantially fulfills these objectives.
The foregoing patent and other information reflect the state of the art of which the inventors are aware and are tendered with a view toward discharging the inventor's acknowledged duty of candor in disclosing information that may be pertinent to the patentability of the present invention. It is respectfully stipulated, however, that the foregoing patent and other information do not teach or render obvious, singly or when considered in combination, the inventor's claimed invention.